1. Field of the Invention
Targeted vesicle/liposomes.
2. Description of Prior Art
The exact name to apply a lipid bladders is an open question. Generally, a vescile is smaller than a liposome, and unilamellar, whereas a liposome is multilamellar. Liposome is a term which wil be used hereafter because it embraces more forms of lipid bladders. This writing will assume a general knowledge of the state of the art of the preparation of liposomes, incorporation of drugs, proteins, and genetic material therein, and targeting. A through presentation of these aspects of liposomes is set forth in a three volume compilation of writings by acknowledged authorities, edited by Gregory Gregoriadis, published by CRC Press, Inc., 2000 Corporate Boulevard, N.W., Boca Raton, Fla., U.S.A., entitled Liposome Technology.
A liposome is generally illustrated by a circular array of symbols representing hydrophilic head groups with lipophilic long chain tail groups. See FIG. 1. It is understood that a liposome is a bladder, roughly spherical in form and subject to distortion to a considerable degree without rupture. It is formed from a mixture of lipids forced into a bladder form by an application of energy, such as by sonication or microfluidic procedures.
The surface generated by the hydrophilic head groups of liposomes has not been of particular concern to prior art development, other than to enclose a core volume space. The surface relationship of the lipid components is all-important in this invention.
The prior art has sufficiently developed the need and use of cholesterol and other ingredients in liposome structure to provide fluidity and charge-charge repulsion to prevent coagulation. The ingredients of a typical prior art liposome, however, may be listed as follows:
A. Preferred bulk bipolar lipid constituents (75-95%) selected from: PA0 B. Minor constituents (0.1-25%) for stability selected from: PA0 2. Dicetyl Phosphate
1. Distearoyl lecithin (DSL) PA1 2. Dipalmitoyl lecithin (DPL) PA1 3. Other lecithins with chain lengths C10-C20. PA1 1. Cholesterol
Liposome technology has advanced the delivery of drugs, diagnostic materials, and cosmetics by capturing the substance of interest in the core volume or wall of the liposome, and using one of the following techniques:
(1) injecting a quantiy of the liposomes into the blood system of a warm blooded host and allowing the substance to escape slowly as the vesicles age and disintegrate.
(2) including an incomplete lipid in the liposome wall, which will cause the wall to leak the core volume contents. The rate of leaking is controllable by varying the amount of the inclusion.
(3) attaching a molecule having an affinity for the target entity, which entity takes in the liposome and utilizes the core volume substance, or, in the case of cosmetics, the targed liposome is held in place on the target while leaking the cosmetic (i.e. breath freshener, etc.). This latter procedure is the subject matter of the copending U.S. Ser. No. 877,862, now U.S. No. 4,767,615 wherein the hydroxyapatite of teeth serves as the anchor target.
There is no known targeting molecule, or other means of binding a liposome to mucin tissue, prior to the present invention.